If we took the precept of non-resistance as an ethical blueprint for general application, we should indeed be indulging in idealistic dreams: we should be dreaming of a utopia with laws which the world would never obey. To make non-resistance a principle for secular life is to deny God, by undermining his gracious ordinance for the preservation of the world. But Jesus is no draughtsman of political blueprints, he is the one who vanquished evil through suffering. It looked as though evil had triumphed on the cross, but the real victory belonged to Jesus. And the cross is the only justification for the precept of non-violence, for it alone can kindle a faith in the victory over evil which will enable men to obey that precept. And only such obedience is blessed with the promise that we shall be partakers of Christ's victory as well as of his sufferings. (Bonhoeffer, The Cost of Discipleship)Pardon my Bennet Brauer quotational-tendencies for a moment, but when I first starting flirting with these understandings of Christ several years ago (just out of seminary), I was told by that I would "get over it," it was "just a phase," that I was "idealistic," etc. I was "out of touch with reality." At one panel discussion on nonviolence, one senior clergy-person said to me: "Yes, but Jeremy, right now there are terrorists hiding in those mountains who have a notion to kill innocent people," as if I didn't think about that.
In the years since, I've been more silent about my understanding of the nonviolent Christ. But my faith conviction in the prescriptive cross has not gone away and has actually only been kindled as I continue to watch the powers of the world bicker and smolder in a struggle of power and control. And by "powers" I don't only mean nation-states, but also the individuals around me (including myself) who so often resort to the ways and means of control to make situations as I would have them to be.
There is no blueprint, really. That would be another Law. Rather, there is a call to follow Jesus in the moments of life. Questions of "What if someone's rapin' your Grandma?" might slightly begin to help flesh out what to do, but only obedience to the will of God by the grace of God will lead us as it did Christ.
So really, it's not about "killing or not killing" at all. If the discussion/debate focuses there, we're doing no better. It's not even a discussion at all, really. And it's certainly not a "position" (of pacifism, or whatever else you want to call it). It's a decision to follow in the path and example of the crucified Christ. Obedience...
The notion of, "Yes, but in real life..." doesn't stop Jesus. We'd all be in big trouble if it did.